1. Field
Embodiments relate to an organic light-emitting device.
2. Description of the Related Art
Organic light-emitting devices (OLEDs), which are self-emitting devices, have advantages such as a wide viewing angle, excellent contrast, quick response, high brightness, and excellent driving voltage characteristics, and can provide multicolored images.
A typical OLED has a structure including, e.g., a substrate, and an anode, a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and a cathode, which are sequentially stacked on the substrate. In this regard, the HTL, the EML, and the ETL may be organic thin films formed of organic compounds.
An operating principle of an OLED having the above-described structure is as follows.
When a voltage is applied between the anode and the cathode, holes injected from the anode move to the EML via the HTL, and electrons injected from the cathode move to the EML via the ETL. The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted.
Luminescent efficiency of an OLED may be categorized into internal luminescent efficiency and external luminescent efficiency. Internal luminescent efficiency is influenced by how efficiently excitons are generated and converted into light in organic layers such as the HTL, EML, and ETL, which are interposed between a first electrode and a second electrode (i.e., between the anode and the cathode). On the other hand, external luminescent efficiency (light coupling efficiency) is influenced by how efficiently light generated in the organic layers is extracted out of the OLED.